The present invention relates to a method of preparing a catalyst for xcex1-olefin polymerization, more particularly, a method of preparing a solid titanium catalyst, the particle size of which can be easily controlled and which is supported by a magnesium-containing supporter.
Until now, many catalysts for olefin polymerization and the polymerization processes for which they are used have been reported. However, in order to improve the physical properties of a produced polymers, or to produce a polymer having special physical properties, development of novel catalysts is urgent.
Magnesium-containing catalysts for olefin polymerization are suitable for gaseous phase polymerization methods and have high catalyst activity and provide polymers of excellent stereoregularity. In catalysts for gaseous phase polymerization methods, catalyst activity and stereoregularity are important in order to reduce cost. In addition, shape, size, size distribution of catalyst particle, etc. are important. To satisfy catalyst activity and stereoregularity in xcex1-olefin polymerization, several studies have been conducted. Thanks to these studies, the elimination of catalyst residue and atactic composition is not required in most of the present, commercial preparation processes of polyolefin, particularly, polypropylene.
However, nowadays, polypropylene having more improved physical properties, particularly stereoregularity is needed. To obtain these polypropylenes, a novel catalyst is needed.
The mean size of a catalyst particle must also be considered. For example, to produce an impact resistant copolymer having a high content ratio of ethylene to propylene, in which the mean particle size is about 1000 xcexcm, a catalyst with a mean particle size of about 30 xcexcm to about 55 xcexcm is required.
With respect to the size distribution of a catalyst particle, a catalyst having a small particle size is problematic for catalyst transfer, while a catalyst with a large particle size is problematic due to the formation of lumps of polymer during polymerization. Thus, a catalyst having a narrow particle size distribution is required.
Furthermore, a catalyst must have excellent resistance against abrasion generated during the polymerization process and must have a sufficiently high bulk density.
Thus, a polymerization catalyst that can be easily prepared and that has an easily controllable particle size is urgently required.
Many catalysts that are based on magnesium-containing titanium for olefin polymerization and many preparation methods thereof have been reported. In particular, many preparation methods have been reported for olefin polymerization catalysts where a magnesium solution is used and in which the particle size is easily controlled. In the presence of hydrocarbon solvent, magnesium compound is reacted with electron donors such as alcohols, amines, cyclic ethers, carboxy oxides, etc. to provide magnesium solution.
Alcohol is used as an electron donor in U.S. Pat. Nos. 4,330,649, 5,106,807 and Japanese Laid-Open Publication No. SHO 58-83006. Preparation methods of magnesium solutions are reported in U.S. Pat. Nos. 4,315,874, 4,399,054 and 4,071,674.
Tetrahydrofuran is a cyclic ether that has been diversely used as magnesium chloride compound (for example, U.S. Pat. No. 4,482,687), as an additive of cocatalyst (U.S. Pat. No. 4,158,642), and as a solvent (U.S. Pat. No. 4,477,639), etc.
U.S. Pat. Nos. 4,347,158, 4,422,957, 4,425,257, 4,618,661 and 4,680,381 disclose preparation methods of catalysts, comprising: (1) adding Lewis acids, such as aluminum chloride, to a supporter, that is, magnesium chloride to provide a mixture and (2) grinding the mixture.
In the aforementioned inventions, high catalyst activity was achieved. However, uniformity in shape and size, narrowness of size distribution, etc. of catalyst particle and excellent stereoregularity were not achieved.
As described in the above, a novel catalyst for olefin polymerization, which can be simply prepared and which has high polymerization activity, large mean particle size, and narrow particle size distribution, the size of which can be regulated, and thus, can be used to provide highly stereoregular polymer is urgently required.
A feature of the present invention is to provide simpler preparation methods of novel catalysts for olefin polymerization. By controlling the solubility of the reactants, the methods produce catalysts having improved activity and narrow particle size distribution. In addition, polymers prepared using the catalysts have more improved stereoregularity.
In accordance with the feature of the present invention, there is provided a preparation method of titanium catalyst for olefin polymerization, comprising (1) preparing magnesium compound solution by dissolving magnesium halide having no reducing ability and IIIA group element compound in a solvent mixture of cyclic ether, at least one alcohol, phosphorus compound and organosilane with or without hydrocarbon solvent; (2) reacting said magnesium compound solution with titanium compound, silicon compound, tin compound or mixture thereof to produce a supporter; and (3) reacting said supporter with titanium compound and electron donor to produce solid complex titanium catalyst, wherein the particle size and particle size distribution of said catalyst are regulated by controlling solubility of the reactants in said steps (2) and/or (3).
Examples of the magnesium halide compounds having no reducing ability are halogenated magnesium, alkylmagnesium halide, alkoxymagnesium halide, aryloxymagnesium halide and the like. These magnesium halide compounds may be effectively used as mixtures of two or more or in complex with other metals.
Examples of IIIA group element compounds, which are used in combination of magnesium halide compounds in the preparation of magnesium compound solution, are boron halide such as boron fluoride, boron chloride and boron bromide; aluminum halide such as aluminum fluoride, aluminum bromide, aluminum chloride and aluminum iodide. The preferred IIIA group element compound is an aluminum halide, most preferably aluminum chloride. The preferred molar ratio of IIIA group element compound to magnesium compound is 0.25 or less. If the ratio exceeds 0.25, the resultant catalyst is of variable size and reduced activity.
Examples of the hydrocarbon solvents which can be used in the preparation of magnesium compound solution include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, decane and kerosene; alicyclic hydrocarbons such as cyclopentane, methyl cyclopentane, cyclohexane, methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; and halogenated hydrocarbons such as trichloroethylene, carbon tetrachloride and chlorobenzene.
To make magnesium halide compound from magnesium solution, as described in the above, a solvent mixture of cyclic ether, at least one alcohol, phosphorus compound and organosilane is used in the presence or absence of hydrocarbon solvent.
Examples of cyclic ethers which can be used in the preparation of magnesium solution according to the present invention include C2-15 cyclic ethers such as tetrahydrofuran, 2-methyl tetrahydrofuran and tetrahydropyran. Preferred example of cyclic ether is tetrahydrofuran. If cyclic ether having carbon atom higher than 15 is used, it is difficult to prepare magnesium solution.
Examples of alcohols which can be used in the preparation of magnesium solution according to the present invention include C1-20 alcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, decanol, dodecanol, octadecylalcohol, benzylalcohol, phenylethylalcohol, isopropylbenzylalcohol, and cumylalcohol. Preferred examples of alcohols are C1-12 alcohols. If alcohols having carbon atom higher than 20 is used, it is difficult to prepare magnesium solution.
Mean size and size distribution of catalyst particle which is prepared differ depending upon the ratio of alcohol to cyclic ether, etc. However, to obtain spherical catalyst having particle size of about 50 xcexcm, the total sum of alcohol and cyclic ether must be about 0.5 moles to about 20 moles, preferably about 1.0 mole to about 20 moles, more preferably about 2.0 moles to about 10 moles per 1 mole of magnesium compound in preparation of said magnesium solution.
If the total sum of alcohol and cyclic ether is less than 0.5 mole per 1 mole of magnesium compound in the said step, it is difficult to prepare magnesium solution. If the total sum of alcohol and cyclic ether is more than 20 moles per mole of magnesium compound in the said step, size of catalyst particle is reduced.
Furthermore, alcohol must be used in an amount of 0.05 mole to 0.95 mole per 1 mole of cyclic ether. If alcohol is less than 0.05 mole per 1 mole of cyclic ether, it is difficult to prepare spherical catalyst. If alcohol is more than 0.95 mole per 1 mole of cyclic ether, the catalyst activity of the resultant catalyst is reduced.
At this moment, as said alcohols, mixed alcohols of C1-3 alcohol having relatively low molecular weight and C4-20 alcohol having relatively high molecular weight is preferable.
Alcohol having relatively low molecular weight must be used in-an amount of 1 mole % to 40 mole %, preferably 1 mole % to 25 mole % based on the total alcohols.
If alcohol having relatively low molecular weight is used in an amount less than 1 mole %, the catalyst activity of the resultant catalyst is reduced. If alcohol having relatively low molecular weight is used in an amount more than 25 mole %, it is difficult to prepare spherical catalyst.
The preferred example of alcohol having relatively low molecular weight is methanol or ethanol, and the preferred example of alcohol having relatively high molecular weight is butanol, isoamyl alcohol or 2-ethylhexanol.
At least one alcohol employed in the present invention, partly or totally, can be used in order to dissolve magnesium compound. Alternatively, firstly, magnesium solution is prepared by dissolving magnesium compound. Secondly, at least one alcohol employed in the present invention, partly or totally, is added thereto.
However, in (2) supporter preparation step, when magnesium solution reacts with transition metal compound to provide solid particles, the total amount of the aforementioned at least one alcohol must be kept constant.
Phosphorus compounds used to prepare the magnesium solution are represented by the following Formula(1):
xe2x80x83PXaRb1(OR2)c or POXdRe3(OR4)jxe2x80x83xe2x80x83(1)
wherein X is a halogen atom;
each of R1, R2, R3 and R4 is independently C1-20 alkyl, alkenyl or aryl;
each of a, b and c is independently an integer of 0-3, provided that a+b+c=3; and
each of d, e and f is independently an integer of 0-3, provided that d+e+f=3.
Examples of phosphorus compounds which can be used in the preparation of magnesium solution according to the present invention include trichlorophosphine, tribromophosphine, diethylchlorophosphite, diphenylchlorophosphite, diethylbromophosphite, diphenylbromophosphite, methyldichlorophosphite, phenyldichlorophosphite, trimethylphosphite, triethylphosphite, trinormalbutylphosphite, trioctylphosphite, tridecylphosphite, triphenylphosphite, phosphorus oxychloride, triethylphosphate, trinormalbutylphosphate, triphenylphosphate and the like. Any other phosphorus compound to satisfy the above Formula (1) is also available. A phosphorus compound may be used in an amount of 0.01 mole to 0.25 mole, preferably 0.05 mole to 0.2 mole per 1 mole of magnesium compound. If the used amount is less than 0.01 mole per 1 mole of magnesium compound, polymerization activity of catalyst is reduced. If the used amount is more than 0.25 mole per 1 mole of magnesium compound, it is difficult to prepare spherical catalyst.
Organosilanes used to prepare magnesium solution are represented by the following Formula(2):
RnSiR4-nxe2x80x83xe2x80x83(2)
wherein R is a hydrogen atom, C1-10 alkyl, alkoxy, haloalkyl or aryl, or C1-8 halosilylalkyl group;
Rxe2x80x2 is halo, C1-10 alkoxy, haloalkoxy or aryloxy, or C1-8 halosilylalkoxy; and
n is an integer of 0-4.
Examples of Organosilanes to satisfy the above Formula (2) include trimethylchlorosilane, trimethylethoxysilane, dimethylchlorosilane, tetraethoxysilane, tetrabutoxysilane, etc.
An organosilane is used as a size-controlling agent in the present invention. It can prevent the production of particles that are too small.
The organosilane is used in an amount of 0.01 mole to 0.25 mole, preferably 0.05 mole to 0.2 mole per 1 mole of magnesium compound. If organosilane is less than 0.01 mole per 1 mole of magnesium compound, the organosilane cannot make its role as a size-controlling agent. If organosilane is more than 0.25 mole per 1 mole of magnesium compound, it is difficult to prepare catalyst particle having the size desired in the present invention.
In order to prepare magnesium solution, it is preferable that magnesium compound is reacted with a solvent mixture of cyclic ether, alcohol, phosphorus compound and organosilane in hydrocarbon medium.
Reaction temperature differs depending upon the species and the amount of cyclic ether, alcohol, phosphorus compound and organosilane. However, reaction can be carried out well at temperature of at least about xe2x88x9225xc2x0 C. to about 200xc2x0 C., preferably about xe2x88x9210xc2x0 C. to about 200xc2x0 C., more preferably about 0xc2x0 C. to about 150xc2x0 C. for about 1 hr to about 20 hrs, preferably about 5 hrs to about 10 hrs.
The magnesium compound solution prepared in aforementioned manner is reacted with transition metal compound, specifically titanium compound, silicon compound, tin compound or mixture thereof to provide a supporter.
An titanium compound which is used in the aforementioned supporter preparation step is in the liquid state and is represented by the following Formula(3):
Ti(OR)aX4-axe2x80x83xe2x80x83(3)
wherein R is a C1-10 alkyl group;
X is a halogen atom; and
a is an integer of 0-4.
Using this titanium compound renders the size of catalyst particle constant and large, distribution of particle size narrow.
The examples of titanium compounds to satisfy the above Formula (3) include tetrahalogenated titanium such as TiCl4, TiBr4 and TiI4; trihalogenatedalkoxy titanium such as Ti(OCH3)Cl3, Ti(OC2H5)Cl3 and Ti(OC2H5)Br3; dihalogenatedalkoxy titanium such as Ti(O(i-C4H9))2Cl2 and tetraalkoxy titanium such as Ti(OC2H5)2Br2; Ti(OCH3)4, Ti(OC2H5)4 and Ti(OC4H9)4. These compounds can be used singly or in combination. Preferably titanium compounds containing halogen atoms, more preferably TiCl4 is used.
The examples of said silicon compound include silicon tetrahalide, silicon alkylhalide and the like. The examples of said tin compounds include tin tetrahalide, tin alkylhalide, tin hydrohalide and the like.
Titanium compound, silicon compound, tin compound, or mixture thereof, employed in order to precipitate magnesium compound solution is used in an amount of about 0.1 to about 200 moles, preferably about 0.1 to about 100 moles, more preferably about 0.2 to about 80 moles per 1 mole of magnesium compound.
When magnesium compound solution is reacted with titanium compound, silicon compound, tin compound or mixture thereof, shape, size and size distribution of the precipitated solid particle (supporter) highly depend on reaction condition.
By reacting magnesium compound solution with titanium compound, silicon compound, tin compound or mixture thereof at a sufficiently low temperature, the immediate production of solid product is prevented. Subsequently, by heating the reaction product slowly, solid composition is produced.
The Solubilities of reactants can be regulated by controlling reaction temperature and pressure.
Temperature of contact reaction is preferably between about xe2x88x9270xc2x0 C. and about 70xc2x0 C., more preferably between about xe2x88x9250xc2x0 C. and about 50xc2x0 C. After the contact reaction, the reaction temperature is slowly elevated to a temperature between about 50xc2x0 C. and about 150xc2x0 C., preferably between about 60xc2x0 C. and about 80xc2x0 C. Then, the reaction is completely carried out for the time between about 30 minutes and 5 hrs.
Reactor pressure is fixed to a value between about 0 bar and about 2 bar (gauge pressure), preferably between about 0.01 and about 0.5 bar (gauge pressure). By fixing reactor pressure to such a low value, evaporated amount of alcohols which dissolve magnesium halide is controlled. In the result, supporter and catalyst are provided with large size and narrow distribution of size. Additionally, the amount of organosilane used as a size-controlling agent is reduced.
The supporter produced in the aforementioned manner is reacted with titanium compound in the presence of an appropriate electron donor to provide catalyst according to the present invention.
Conventionally, this reaction is comprised of two steps: (1) reacting magnesium supporter with titanium compound, optionally together with an electron donor, and subsequently separating solid composition; and (2) reacting said solid composition with titanium compound and an electron donor once more, separating solid composition, and subsequently drying solid composition.
Alternatively, magnesium supporter is reacted with titanium compound in the presence or absence of hydrocarbon solvent or halogenated hydrocarbon solvent for appropriate hours. And then, an electron donor is introduced thereto and the reaction is carried out.
It is desirable to conduct reaction at a temperature of about 90xc2x0 C. to about 120xc2x0 C. and at a gauge pressure of about 0 bar to about 2 bar.
The examples of said titanium compounds include titanium halide, C1-20 halogenatedalkoxy titanium, or mixture thereof. Preferably, titanium halide or C1-8 halogenatedalkoxy titanium, more preferably, titanium tetrahalide is used.
According to the present invention, titanium catalyst for olefin polymerization having mean particle size of 30 xcexcm-120 xcexcm is prepared.
Catalyst prepared according to the present invention, directly or prepolymerized, can be effectively used in polymerizing propylene. Especially, this catalyst is useful in copolymerizing olefins such as ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene and 1-hexene and copolymerizing monomers having polyunsaturated compounds such as conjugated or unconjugated dienes.
Now, the preferred embodiments of the present invention will be described in detail by the following Examples without limiting the scope of the invention in any way.